Update eip-1577.md (ethereum#1611)

EIPS/eip-1577.md

@@ -24,13 +24,21 @@ The field `contenthash` is introduced, which permits a wide range of protocols t
 
 The fields `content` and `multihash` are deprecated.
 
-The encoding of the value depends on the content type specified by the protoCode; for instance, types in the range 0x00-0xf0 are encoded using [multihash](https://github.com/multiformats/multihash), meaning their format is specified as follows:
+The value returned by `contenthash` MUST be represented as a machine-readable [multicodec](https://github.com/multiformats/multicodec). The format is specified as follows:
+
+```
+<protoCode uvarint><value []byte>
+```
+
+protoCodes and their meanings are specified in the [ensdomains/multicodec](https://github.com/ensdomains/multicodec) repository.
+
+The encoding of the value depends on the content type specified by the protoCode; for instance, types in the range 0x00-0xf0 are encoded using [multihash](https://github.com/multiformats/multihash), meaning their value is formatted as follows:
 
 ```
 <varint hash function code><varint digest size in bytes><hash function output>
 ```
 
-When resolving a multiaddr, applications MUST use the protocol code to determine what type of address is encoded, and resolve the address appropriately for that protocol, if supported.
+When resolving a `contenthash`, applications MUST use the protocol code to determine what type of address is encoded, and resolve the address appropriately for that protocol, if supported.
 
 ### Example